“Big news,” the Texas congressman wrote on his Facebook page Tuesday. “I have decided not to seek reelection for my House seat in 2012 and will focus all of my energy on winning the presidency.”

The retirement will take the country’s most prominent libertarian voice out of Washington, after years of redefining conservative politics. Opposing increases in the debt ceiling, supporting a more isolationist foreign policy, abolishing the Fed — all longtime Paul mainstays that would have been laughed off only a few years ago — are now well within the Republican mainstream. And it provides yet another signal that Paul plans to take a more intense approach to the 2012 campaign — he’s already stepped up his presence on the trail in Iowa and New Hampshire — adding to a strong fundraising operation that raised $4.5 million in the second quarter. He’s already aggressively deploying that haul, which outpaced big name contenders like Tim Pawlenty and Newt Gingrich, with a $75,000 statewide radio ad buy in Iowa announced last week.

As for whether voters will be disappointed to see Paul give up his seat in Washington, Paul’s Iowa campaign Vice Chairman A.J. Spiker said the news won’t likely have an impact.

“Congressman Paul is not the type of Washington politician that really cares if he owns a seat,” Spiker said. “He’s focused on the future of the country and right now, things are looking really bleak.”

Paul’s supporters see the announcement as actually boosting his credibility with his core support of libertarians and tea party activists.

“I think Ron Paul’s decision to not run amplifies his commitment and message. He cannot be accused of positioning himself for another congressional run or just being a messenger but a presidential candidate committed to leading America out of its wilderness of debt,” said Drew Ivers, chairman of Paul’s Iowa campaign.

Paul served five terms in the House before retiring ahead of the 1984 election. He ran for president as the Libertarian Party candidate in 1988, then returned to Congress in 1996, where he grew into the leading voice of libertarian politics in Washington and a harbinger of policy positions that have moved into the mainstream. And he’s developed a fiercely devoted if narrow following, along with much of the credit for seeding the tea party movement.

“He pointed to problems people weren’t ready to look at, but within the next few years the problems he had pointed to became clear,” said David Boaz, executive vice president of the libertarian Cato Institute. “Maybe the party would have moved in that direction without Ron Paul, but he certainly provided an impetus and a focus, and he raised a banner to which people could rally if they were worried about these issues.”

Attention will now turn to his son, freshman Kentucky Sen. Rand Paul, who toyed with a presidential run himself earlier this year and is a tea party star in the Senate. The younger Paul’s willingness to work with colleagues holds out the promise that he can have a greater impact in pushing libertarian policies than his father ever had.

“He’s learned to work with his caucus leader and the rest of the caucus in a way that I think Ron Paul never put much emphasis on,” Boaz said of the freshman senator. “But in terms of the big issues that he’s talking about, he’s clearly following in his father’s footsteps.”

Although another of Paul’s sons, Robert — who lives in Texas but not in the district — has expressed his own political ambitions, at least for now, it doesn’t look like there will be another Paul in the expected competitive race for the House seat.

“This is not a seat that’s been open or in play for many, many years,” said Chris Perkins, a longtime Texas pollster. “The opportunity here is for someone to hold a strong Republican seat for pretty much as long as you want to hold it. It could get pretty crowded.”

Republican operatives quickly turned to a trio of state lawmakers who could run in what’s expected to remain a very GOP-friendly, Houston-area seat, even after the new round of redistricting. State Sen. Mike Jackson’s legislative district in Brazoria County encompasses much of the new congressional district’s Republican base. State Rep. Dennis Bonnen is serving his eighth term in Austin but is still seen as a potential rising star. And state Rep. Larry Taylor has a district packed with GOP primary voters in Galveston County and a close relationship with the congressional delegation because of his work as state House caucus chair.

“It has a bigger impact in state politics than it does on his campaign,” said James Henson, director of the University of Texas’s Politics Project. “There is a lot of pent-up demand among Texas elected officials to move up in the world, and there’s a considerable cascade effect created by an open congressional seat.”